Note 6 - Employee Benefit Plans - Benefit Obligation, Fair Value of Plan Assets, Funded Status and Liability of Swiss Plan (Details) - Swiss Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 25, 2021	Dec. 26, 2020
Benefit obligation at beginning of year	$ (28,765)	$ (31,039)
Service cost	(954)	(1,223)	$ (1,310)
Interest cost	(56)	(61)	(67)
Actuarial gain	6,043	1,179
Participant contributions	(1,459)	(1,780)
Benefits paid	378	436
Plan change	397	1,076
Settlements	2,426	1,653
Foreign currency exchange adjustment	362	994
Benefit obligation at end of year	(21,628)	(28,765)	(31,039)
Fair value of plan assets at beginning of year	18,919	18,756
Return on assets, net of actuarial loss	119	207
Employer contributions	831	878
Participant contributions	1,459	1,780
Benefits paid	(378)	(436)
Settlements	(2,426)	(1,653)
Foreign currency exchange adjustment	(113)	(613)
Fair value of plan assets at end of year	18,411	18,919	$ 18,756
Net liability at end of year	$ (3,217)	$ (9,846)